Biomedical Engineering Reference
In-Depth Information
Biomechanics (ISB) [WU 02] (see Chapter 3). However, for
the ankle joint (foot/leg), a “ZYX” sequence is considered to
best represent inversion-eversion [BAK 03]. The net joint
moment, i.e. the resulting moment from all joint structures
(muscles, joints surfaces, ligaments, etc.) on a point
coinciding with the joint center, is calculated from the free
body diagram of each lower limb segment using the
equations of Newton-Euler [DUM 04], then expressed in
the joint coordinate system (DES 10]. For this calculation,
the body segment parameters are defined using the
regressions of Jensen [JEN 89]. Joint power is
then calculated using the scalar product of the net joint
moment and the corresponding joint angular velocity. All
these parameters are converted into dimensionless
quantities according to the recommendations by Hof
[HOF 96].
To overcome the effect of walking speed, the range of
dimensionless speeds of the available measurements [0.09-
0.71] is reduced to [0.35-0.49], representing approximately
51% of the initial figure, so that there are no differences in
speed between age groups (Kruskal-Wallis test,
p
< 0.05).
5.
1.2
.
Results and discussion
For all kinematic and dynamic variables, the peaks of
evolution curves and amplitudes over the gait cycle were
analyzed (Figures 5.2 and 5.3). These values were compared
between the age groups (giving a total of 15 comparisons) to
reveal the age-related differences: Kruskal-Wallis test (
p
<
0.05), and Kolmogorov-Smirnov
post-hoc
test with Bonferroni
correction,
p
< 0.003 (i.e.
p
< 0.05/15).
The results reveal differences for almost all values
between the youngest age group (1-2 years old) and the
other groups. For the ankle joint, apart from some
